the most common benign solid breast tumor noninfiltrative lesion compresses surrounding tissues as it grows within normal tissue planes the pseudocapsule of a fibroadenoma represents the leading edge of compressed breast tissue surrounding the mass

estrogen-induced tumor overgrowth of connective and glandular tissues within a lobule

most common breast tumor in females under the age of 30; more common than cysts in this age group develops in females of reproductive age; rarely after menopause easily moveable; firm, rubbery, palpable mass single or multiple; unilateral or bilateral higher incidence of multiple, bilateral tumors in black women tumors typically > 3 cm in size may grow rapidly during pregnancy regress in size after menopause; may enlarge in women on HRT older fibroadenomas can undergo hyalinization, degeneration, sclerosis, necrosis, and calcification

low-density to high-density - radiopaque - water-density mass circumscribed, smooth margins round, oval, or lobulated contour with distinctive notch thin radiolucent halo sign occasional coarse popcorn-like or thin rim [eggshell] calcifications indicate degenerative changes

wider-than-tall, ellipsoid shape; may show macrolobulation oriented with long-axis parallel to the skin smooth, well-circumscribed margins; thin echogenic pseudocapsule mildly hypoechoic or isoechoic when compared to fat usually displays homogeneous echo pattern normal sound transmission or mild sound enhancement thin refractive edge shadowing on occasion, an internal fibrous septation may be seen as a thin, echogenic line that horizontally traverses the fibroadenoma. This non-enhancing internal septa is a MRI feature of a fibroadenoma. frequently show some peripheral and internal blood flow depending on tumor size and Doppler sensitivity typically measure less than 3 cm in size

fibroadenomas can be firm or mildly compressible with transducer pressure and will not displace or indent adjacent structures. a fat lobule will be more compressible and will not indent fascial planes and muscles

typically measure less than or equal to 3 cm can grow rapidly during pregnancy and lactation larger, rapidly growing masses should be differentiated from giant or juvenile fibroadenoma, lactating adenoma, phyllodes tumor, PASH, or medullary carcinoma more likely to show more than 3 macrolobulations more likely to be heterogeneous and show evidence of degeneration, sclerosis, or necrosis. Hyalinized fibroadenomas can display shadowing and some marginal irregularity

Tend to regress in size and/or calcify. Coarse popcorn-like calcifications on a mammogram are characteristics of a degenerating fibroadenoma. thin egg-shell calcifications occur along the tumor rim. calcified fibroadenomas display partial or complete acoustic shadowing and may mimic a suspicious lesion

in some atypical cases, fibroadenomas can show internal epithelial proliferative changes that lie within the spectrum of fibrocystic change. such changes can appear as small cystic areas, microcalcifications, or as a focal area of hyperechogenicity. these features may indicate internal apocrine metaplasia with cyst formation, epithelial calcifications, or sclerosing adenosis reported to show a slight increased relative risk for developing breast cancer a rapidly growing fibroadenoma with internal cystic spaces should be biopsied to differentiate from phyllodes tumor or medullary carcinoma

typically develops in an adolescent female before 20 years of age accounts for 5-10% of fibroadenomas in this age group non-tender, well-circumscribed mass grows rapidly and is often large at time of presentation tumor often exceeds 5 cm in size and can distort the skin newer terminology for this giant type of fibroadenoma is a fibroadenoma with highly cellular stroma often homogeneous and shows distal sound enhancement Doppler typically shows prominent vascularity